The human spine is mostly comprised of individual vertebral bones stacked on top of one another. The spine must perform two tasks: support the weight of the head and torso while at the same time allowing the head and torso to move. The design of the spine is quite ingenious in this regard, since the individual bones allow for bending and turning while the stacked configuration provides sturdy support.
Each of the upper 24 vertebral bones has an intervertebral disc. Intervertebral discs have a solid outer ring and a soft, pliable center. Given their anatomical structure and placement between vertebrae, intervertebral discs act like shock absorbers. They also allow vertebral bones to move past one another so that humans can twist, bend, and move the torso from side to side.
Essentially everyone will have changes to their intervertebral discs as they age. By the time someone reaches age 30, the normally pliable intervertebral discs start to become fibrous and stiff. Unfortunately, this is part of growing older. On the other hand, some people will have the decidedly abnormal condition called degenerative disc disease.
Degenerative disc disease is a deterioration of the intervertebral disc(s).
Degenerative disc disease progresses much more rapidly than age-related changes in the spine. It can be divided into three stages:
- Abnormal function
- Spinal instability
- Maladaptive re-stabilization
In the earliest stages of degenerative disc disease, the tough outer ring (called the annulus fibrosus) may show signs of wear and tear (literally). Since this outer ring is full of nerve endings, the condition can be quite painful. As the outer ring tears, the pliable inner core (called the nucleus pulposus)of the intervertebral disc can extend beyond the outer ring. You may also notice that you have difficulty moving your back or neck when that movement involves the affected discs. This is the abnormal function of degenerative disc disease.
Spinal instability leads to a number of changes, both in the spine and in the way the person carries him or herself. Because of the pain and lack of mobility, patients tend to contract muscles that they normally do not use or they avoid making movements to minimize pain. The spine also tries to heal itself, but does not do a very good job. As the intervertebral discs scar and shrink, the spaces between vertebrae become smaller. The spinal column actually becomes relatively unstable as thevertebral bones can slide across one